B.J. Fogg's students at Stanford have created a fun set of short videos about the use of persuasion in popular Web 2.0 sites. The videos are here: http://www.captology.tv.
I have only watched a small set of the videos, but I particularly enjoyed ShaneWalker112's piece on starting up a social network on sites like linkedin.com. Videos about Web sites can be dull, but ShaneWalker112 uses Lionel Richie tunes to nice comedic effect. Overall, I was very impressed by the quality and information content of the videos that I watched.